Chemistry and Physics. 67 



error in view of the fact that Mr. Glazebrook (Proc. Cambr. Phil. 

 Soc, iv, p. 166) expressly states that his results are the same as 

 those of Lorentz, Fitzgerald, and J. J. Thomson. We have spent 

 much fruitless labor in trying to discover where and how the ex- 

 pressions were obtained which are attributed to Glazebrook, but 

 in which the notation has been altered. They ought to come 

 from Glazebrook's equations (24)-(27) {loo. cit.), but these appear 

 identical with Lorentz' s equations (58)-(61) (Zeitschrift f. Math. 

 u. Phys., xxii, p. 27). They might be obtained by interchanging 

 the expressions for vibrations in the plane of incidence and at 

 right angles to it, with two changes of sign. 



The reader must be especially cautioned concerning the state- 

 ments and implications of what has not been done in the electro- 

 magnetic theory. These are such as to suggest the question 

 whether the author has taken the trouble to read the titles of the 

 papers which have been published. We refer especially to what 

 is said on pages 248, 249 concerning absorption, dispersion, and 

 the magnetic rotation of the plane of polarization. 



In the Experimental Part, with which the treatise closes, we 

 have a comparison of formulas with the results of experiments 

 by the author and others. The author has been particularly suc- 

 cessful in the formula for dispersion. In the case of quartz (p. 

 545), the formula (with four constants) represents the results of 

 experiment in a manner entirely satisfactory through the entire 

 range of wave-length from 2*14 to 0*214. Those who may not 

 agree with the author's theoretical views will nevertheless be glad 

 to see the results of experiment brought together, and, so far as 

 may be, represented by formulas. j. w. G. 



10. The magnetic and electrical properties of the iron carburets; 

 by C. Bartts and V. Stkotthal. Bull. 14, IT. S. Geological Sur- 

 vey, Washington, 1885. — The authors give in complete form the 

 results of about five years of research on the properties of the 

 iron-carburets. Proposing to investigate the relation between 

 intensity of magnetism, hardness, figure and carburation of steel, 

 they find during the course of the investigation that the end in 

 view must remain unattainable as long as the physics of the ope- 

 ration of tempering have not been rigidly discussed. The results 

 of these auxiliary experiments are contained in the first three 

 chapters of the book. The general deduction is this, that if one 

 and the same steel rod pass from an initial hard to a final soft state, 

 any intermediate degree of hardness can be defined with extreme 

 accuracy, by using as a means of discrimination either the ther- 

 mo-electric power or the electrical resistance of the rod. Chap- 

 ter I, therefore, treats of the relation between temperature and 

 resistance in case of any given carburet and leads to chapter II, 

 in which the electrical behavior of tempered steel is minutely an- 

 alyzed. This chapter is fundamental. Such facts as essentially 

 sustain the argument underlying the whole of the subsequent 

 work, ai*e therefore emphasized by many experimental data. The 

 annealing effect of any temperature acting on glass-hard steel is 



